Antibacterial activity of the probiotic candidate Lactobacillus gasseri against methicillin-resistant Staphylococcus aureus

Takumi Ishikawa (1,2), Susumu Imai (2), Takuya Nakano (1,2), Tomohiko Terai (3), Takekazu Okumura (3), Nobuhiro Hanada (2), Hiroshi Kawahara (1)

(1) Department of Dental Anesthesiology, Tsurumi University School of Dental Medicine, (2) Department of Translational Research, Tsurumi University School of Dental Medicine, Yokohama, (3) Microbiological Research Department, Yakult Central Institute, Kunitachi, Yakult Honsha Co., Ltd., Tokyo, Japan

Purpose: The objective of this study was to verify growth suppression of methicillin-resistant Staphylococcus aureus (MRSA) involved in ventilator-associated pneumonia (VAP) aggravation by the probiotic candidate bacterium Lactobacillus gasseri (L. gasseri) in the oral cavity.

Materials and Methods: L. gasseri YIT 12321 (Lg YIT 12321) and MRSA JCM 8702 (MRSA-JCM) were used as test bacteria. Both Lg YIT 12321 and MRSA-JCM were cultured in lactobacilli MRS medium, and MRSA-JCM was also cultured in TS medium anaerobically at 37˚C for 18-24 hours. The antibacterial activity of Lg YIT 12321 against MRSA-JCM was examined by competition assay and radial diffusion assay (RDA). A fraction obtained from the Lg YIT 12321 culture supernatant by 50% (w/v) saturated ammonium sulfate (50% sat. ammonium) precipitation was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).

Results: In the competition assay, inhibition of MRSA-JCM proliferation by Lg YIT 12321 was observed. Moreover, it was confirmed that the growth of MRSA-JCM was inhibited by neutralized culture supernatant of Lg YIT 12321 in the RDA, suggesting that the growth of MRSA-JCM was suppressed by an antibacterial substance produced by Lg YIT 12321.

Conclusion: Lg YIT 12321 is a candidate probiotic that produces a class II bacteriocin that suppresses the growth of MRSA-JCM.
(Asian Pac J Dent 2020; 20: 1-8.)
Key Words: Bacteriocin, L. gasseri, MRSA, probiotics, ventilator-associated pneumonia